ZOOLOGY. MOLLUSCA. 201 



lltiiv hj/polcpla. Shuttleworth, Diagnosen ncuer Mollusken, 

 no. 6, from the Born. Mittlieil., March, 1854, p.' 12!). 



The group Mia-ophysa, in which I liave placed this shell, has 

 beon a stumbling block to most of the authors who have rec- 

 ognizod it. It consists of small, umbilicated, thin, hyaline 

 hoUs, with shai-p lip to the lunar-oval aperture, convex whorls 

 and impressed sutures. There is little in all this to separate it 

 from certain forms of Zonitcs [Z. minusculus, for exanii)le). 

 But tho Zonitcs have narrow aculeate marginal teeth to the 

 radula, wliile these sliells, typified by II. Boothiana Pfr., have 

 the dentition of Palnla. Tho marginal teeth are low and wide, 

 with several denticles. 



s 



